The object of the invention comprises a method of feeding a fuel gas into the reaction shaft of a suspension smelting furnace.
The invention also relates to a concentrate burner for feeding a reaction gas and fine-grained solid matter into the reaction shaft of the suspension smelting furnace.
The invention also relates to use of the method and the concentrate burner.
The invention relates to the method that takes place in the suspension smelting furnace, such as a flash smelting furnace, and to the concentrate burner for feeding the reaction gas and fine-grained solid matter into the reaction shaft of the suspension smelting furnace, such as the flash smelting furnace.
The flash smelting furnace comprises three main sections: a reaction shaft, a lower furnace and an uptake. In the flash smelting process, the pulverous solid matter that comprises a sulphidic concentrate, a slag forming agent and other pulverous components is mixed with the reaction gas by means of the concentrate burner in the upper part of the reaction shaft. The reaction gas may comprise air, oxygen or oxygen-enriched air. The concentrate burner comprises normally a feeder pipe for feeding the fine solid matter into the reaction shaft, where the orifice of the feeder pipe opens to the reaction shaft. The concentrate burner further comprises normally a dispersing device, which is arranged concentrically inside the feeder pipe and which extends to a distance from the orifice of the feeder pipe inside the reaction shaft and which comprises dispersing gas openings for directing a dispersing gas to the fine solid matter that flows around the dispersing device. The concentrate burner further normally comprises a gas supply device for feeding the reaction gas into the reaction shaft, the gas supply device opening to the reaction shaft through an annular discharge opening that surrounds the feeder pipe concentrically for mixing the said reaction gas that discharges from the annular discharge opening with the fine solid matter, which discharges from the middle of the feeder pipe and which is directed to the side by means of the dispersing gas. The flash smelting process comprises a stage, wherein the fine solid matter is fed into the reaction shaft through the orifice of the feeder pipe of the concentrate burner. The flash smelting process further comprises a stage, where the dispersing gas is fed into the reaction shaft through the dispersing gas openings of the dispersing device of the concentrate burner for directing the dispersing gas to the fine solid matter that flows around the dispersing device, and a stage, where the reaction gas is fed into the reaction shaft through the annular discharge opening of the gas supply device of the concentrate burner for mixing the reaction gas with the solid matter, which discharges from the middle of the feeder pipe and which is directed to the side by means of the dispersing gas.
In most cases, the energy needed for the melting is obtained from the mixture itself, when the components of the mixture that is fed into the reaction shaft, the pulverous solid matter and the reaction gas react with each other. However, there are raw materials, which do not produce enough energy when reacting with each other and which, for a sufficient melting, require that fuel gas is also fed into the reaction shaft to produce energy for the melting. After production breaks, it may also be necessary to temporarily bring more energy in the form of fuel gas to the reaction shaft to properly initiate the reactions. For the time of production breaks, it may also be necessary to temporarily bring more energy in the form of fuel gas to the reaction shaft to maintain the temperature in the reaction shaft.
Various solutions are known for feeding the fuel gas into the reaction shaft.
In a known solution, the fuel gas is fed through a channel, which runs in the middle of the dispersing device of the concentrate burner, directly downwards into the reaction shaft. The disadvantages of this solution are its weak and local performance in the reaction shaft.
In another known solution, the fuel gas is fed into the reaction shaft through separate fuel gas feeding members that are arranged in the inner structure of the reaction shaft or attached to the reaction shaft itself. One disadvantage of this solution is that the separate fuel gas feeding members cause point-form thermal stress to the structure of the reaction shaft in the spot, wherein the separate fuel gas feeding member is arranged, and the point-form thermal stress wears the structures of the reaction shaft.
The patent specification WO 2009/030808 presents a concentrate burner.